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Spindle RPM Question(s)
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Author:  Anthony Lembo [ Tue Dec 02, 2008 6:43 pm ]
Post subject:  Spindle RPM Question(s)
Hi everyone.

I'm in the process of shopping for a CNC, and I have a question for the gurus. :D

Would there be a major advantage in opting for a 24k RPM spindle over an 18k RPM one? The smallest tool size I'll be using will be for fret slots (.023ish), or possibly smaller for the occasional circuit board. There is a not a huge difference in cost ($200), but is it even worth it?

I've also been researching the Wolfgang spindle - the circuit boards will be fine with this, but what about fret slotting?

Thanks for your help. :)

Anthony
Author:  npalen [ Wed Dec 03, 2008 4:03 pm ]
Post subject:  Re: Spindle RPM Question(s)
Hello Anthony
Other's with more CNC knowledge will be along but I'll give you my two cents worth.
I would opt for the higher RPM spindle for endmills that small to get a decent surface speed and feedrate capability.
You may end up doing a lot of small tool work for inlays etc. also.
Others here have experience with the Wolfgang and can probably help you there also.
Good luck!
Nelson
Author:  Bob Garrish [ Wed Dec 03, 2008 4:21 pm ]
Post subject:  Re: Spindle RPM Question(s)
Depends on how much you're spending on the CNC. If I could get 6K RPM for $200 I'd pay it in a second. Of course, on a VMC an extra 5K RPM will cost $5-10K! The higher your spindle speed, the more fragile your bearings are, etc, but most guys don't really run their machines 'production hard' anyhow...

Depending on how smoothly your machine moves you may or may not be able to translate all the extra RPMs you get from a Wolfgang spindle into speed for fret slotting, but they'll certainly help either way. Those little mills like an RPM buffer.
Author:  Brad Way [ Wed Dec 03, 2008 6:14 pm ]
Post subject:  Re: Spindle RPM Question(s)
Anthony...what kind of CNC router are you looking at?
Author:  Parser [ Wed Dec 03, 2008 6:44 pm ]
Post subject:  Re: Spindle RPM Question(s)
It depends on what you would like to use it for. Do you want to carve necks or do you want to cut inlay? You can cut inlay with a neck carving machine...but you're really pushing it if you want to carve a neck on a machine that's setup better for shell. Neck carving = Horsepower, Inlay cutting = RPM...
Author:  Anthony Lembo [ Wed Dec 03, 2008 7:02 pm ]
Post subject:  Re: Spindle RPM Question(s)
Thanks for the replies everyone. :)

Brad - I'm looking at a K2. The 3925.

Parser - I want the ability to do both. :D

The spindle is 3hp, so it should handle necks just fine. I just didn't know if I would be better of saving a couple of hundred bucks to put towards the Wolfgang, or if the 24k RPM will handle the small stuff ok. I guess I can always add a Wolfgang later.

Thanks again everyone.

Anthony
Author:  Parser [ Thu Dec 04, 2008 7:43 pm ]
Post subject:  Re: Spindle RPM Question(s)
I have the K2 Kg3925...i use it with the porter cable 892 (@ 2.25 HP/23000 rpm). I opted for the extended Z; 8" of capacity.

I carve necks using the machine but you definitely have to be strategic using something this low powered. The machine itself is too flimsy to run at much higher than 30 ipm doing a carve through any amount of material. Thing small passes in order to get your speed decent...

Running those small bits, the other things that comes into play is runout. I'm not familiar with the spindles you mentioned, but I would go with the one with the best runout characteristics. With the small end mills, I believe this is just as important as spindle speed. More runout = more broken bits!
Author:  Bob Garrish [ Fri Dec 05, 2008 11:02 am ]
Post subject:  Re: Spindle RPM Question(s)
Runout on small bits is absolutely killer. Even up to 1/8" it can be a big issue, so you can imagine what it does to a 0.025" cutter (or even the 0.0156" and 0.01" ones, if you end up going that small!). For inlay, and considering the cost of tiny cutters, I'd absolutely recommend either getting a spindle with low runout (as opposed to a router) or a sub-spindle with low runout (like the Wolfgang).

BTW, the cutters from Precisebits are absolutely worth the cost if you have a low-runout setup. If you don't, then buy the cheapest ones you can find because you'll be replacing them before they get dull anyhow.
Author:  Anthony Lembo [ Sat Dec 06, 2008 1:22 pm ]
Post subject:  Re: Spindle RPM Question(s)
It sounds like the 24k RPM is the way to go. Thanks a bunch for your help everyone. :)

Oh - and thanks for the tip on Precisebits Bob - good stuff.

Anthony
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